The invention relates to an arrangement for the control of electrically controllable appliances, particularly electric cookers.
The preferred field of application for the invention is the control of electrically operated domestic appliances, particularly electric cookers, e.g. those having a glass ceramic cooking area and/or an electric oven. Such control arrangements have at least one manually operable control or control element placeable or placed on an outside of a plate of the appliance and which is held on or close to the plate by an associated holding device. There is also a sensor device intended to cooperate with a control device of the appliance for determining the position and/or position change of the control element. By appropriately moving the control element a desired switching state can be set.
A known and very frequently used construction of such control elements or controls is constituted by knobs. Knobs can be placed individually or in a group on a front panel of a cooker or the like below the normal working level. As a result of this arrangement the scales on such knobs are sometimes difficult to read. There is also a risk of the knobs being reached and operated by small children. Keeping clean can also constitute a problem. A large amount of space is generally required for the fitting of the knobs with corresponding mechanical holding devices.
These problems can be partly removed by the placing of the knobs on the top of the appliance. EP 797 227 shows for this purpose a construction particularly suitable for fitting to glass ceramic plates, in which the knobs are secured magnetically through the plate by means of a holding magnet placed on the underside of the glass ceramic plate. Knobs must have a certain minimum height, so that they can be easily turned and gripped by hand. Thus, they can interfere with the handling of cooking utensils in the cooking area. In addition, a free hand is necessary for their operation, so as to be able to securely hold and turn the knob.
Another known class of control elements is constituted by sliders, which are used for setting a desired operating state starting from a usually stop-limited, fixed neutral position can be slid over a clearly defined sliding or displacement path into an end position corresponding to the desired switching state. Examples of such sliders are described in European patent application EP 497 191 and U.S. Pat. Nos. 3,711,672 and 3,852,558. The precise setting of a desired end position can be problematical, because an energetic operator can slide it beyond the end position and a subsequent correction can be necessary. Moreover, both with the known knobs and also the sliders, on the way to the desired end position it is necessary to pass through all the intermediate positions and at least briefly switching states associated therewith may be assumed or activated.
The problem of the invention is to provide an arrangement for the control of electrically controllable appliances which, in the case of easy operation, permits a reliable setting of a desired switching state.
According to the invention this problem is solved by an arrangement having the features of claim 1. Further developments of the invention are given in the subclaims, whose wording is made by reference into part of the description.
An inventive control arrangement is characterized in that at least one control element is constructed as a slider automatically returning to an off or rest position and which is slidable along the plate in at least one sliding direction. Such a slider or sliding key creates the possibility of using a sliding process as such as a switching event, without it being a question of the precise maintaining of a sliding path corresponding to this state e.g. for setting a desired switching state. A self-resetting slider must, unlike in the case of conventional knobs or path sliders, not necessarily be gripped and moved by the fingers of a hand for its operation, but can instead be operated e.g. with the elbow, forearm or back of a hand. This facilitates operation, particularly if e.g. both hands are needed for holding a saucepan or the like. An inventive sliding key is also particularly advantageously adapted to a digital processing of sensor signals or control signals, because a controlling adjusting process with subsequent return to the rest position can be treated as an event e.g. detectable by a digital counter. There is no need to use analog/digital converters, which must be used with conventional knobs or sliders for generating digitally processable signals.
Certain advantages of the invention are usable with sliding keys controlling slidable in only one sliding direction. According to a preferred further development the control element can be slid in controlling manner in at least two different sliding directions, starting from the rest position, for generating at least two different control signals. Thus, the number of settings possible with a single control element is advantageously increased, because the sliding direction can now be used as a further input parameter for control purposes. Although the individual sliding directions can be oriented in random, optionally very small planar angles parallel to the plate surface, it is preferable if there are at least two antiparallel switching displacement directions, so that it is possible to implement a uniaxial, bidirectional sliding key. Multiaxial displaceable sliders are also possible. Thus, in an embodiment and starting from a common rest position, four controlling displacement directions oriented at right angles to one another are provided, so that a biaxial, bidirectional sliding key can be obtained. Sliding or displacement directions can also be arranged in a radial or fan-like manner and it is appropriately ensured that displacement directions in the plane are far enough apart in order to prevent an accidental setting by the user of an undesired switching state. A key displaceable in several, preferably coplanar displacement directions inter alia permits the selection of switching targets via the choice of the displacement direction. A direct switching e.g. between different operating modes of an oven is possible, without it being necessary on the switching path to also switch in at least briefly undesired modes. This protects both the heating-active components and also the control components and avoids in the case of switching processes for higher electric currents difficultly avoidable repercussions of the switching on the main supply.
The use of a sliding event for the control of the appliance can take place in different advantageous ways as a function of the particular circumstances. Thus, for reasons of operational safety and to avoid incorrect actuations, it is advantageous for the sensor device to be coupled or cooperate with the control device in such a way that a controlling displacement only occurs on exceeding a minimum displacement range in the particular displacement direction. This creates a lower threshold for a controlling displacement, so that in the case of an unintentional small movement of the actuating element and/or with a movement in a direction diverging from an intended displacement direction no control effect occurs. This ensures that only desired, targeted displacements give rise to a control effect.
According to a further development, the sensor device is so coupled with the control device that in the case of a controlling displacement on exceeding a minimum displacement range a single control signal is generated and preferably in certain limits independently of the displacement range achieved with maximum deflection from the rest position. Thus, an on/off information can be associated with the particular displacement direction which can be particularly easily digitally processed. Thus, e.g. with a particular displacement or sliding direction can be associated a specific oven function (hot air, grill, bottom heat, top heat, top and bottom heat, circulating air, etc.), which can in each case be associated by means of the keying or sliding process in the associated displacement direction. In a cooking area circuit it is e.g. possible to preselect a particular parboiling stage, e.g. with 60 or 80% of the rated power.
It is also possible for the coupling to be designed in such a way that with a controlling displacement a number of control signals is generated as a function of a holding time in the displaced or deflected state. Such a time-dependent control can e.g. be used for the stepwise passage through menu points of a presettable control menu or for the stepwise setting of temperature values or for operating mode selection in a preset sequence.
It is also possible to design the control in such a way that a control signal is generated as a function of the number of successive, controlling displacements in a preset displacement direction. Thus, by means of multiple displacements a user can set a desired control state and appropriately the number of displacements or keying processes is counted and a further keying process only increases the same if this takes place briefly within a presettable time limit following a preceding keying process.
The switching state reached can be rendered easily detectable for the user, e.g. by an optical display and/or acoustically.
Any suitable holding device can be used for maintaining the control element on the plate, particularly one having positively and/or nonpositively acting mechanical holders and/or guides. In order to avoid such elements, particularly on the outside of the plate, in a preferred embodiment the holding device is located on the inside of the plate opposite to the control element, so that it cannot cause interference on the operation side. Preferably the holding device is constructed as a device for producing a preferably magnetic field of force, which acts on the control element in non-contacting manner, particularly through the plate and maintains the same on or in the vicinity of the plate. Preferably a control element is held on the plate exclusively by the force of the field of force, so that no further holding devices are required. The control element can be held in an exclusively non-contact manner in the vicinity of the point where it is to be operated and for e.g. cleaning purposes and without the aid of tools can be removed from the plate. The plate, e.g. a glass ceramic plate, preferably has no openings, passages, depressions, mounting supports, etc., which could act as dirt traps or through which dirt could penetrate into the vicinity of the inside of the plate. The plate can be made from a material such that the force field lines pass in substantially unattenuated manner through it. The control element can e.g. engage on the outside, i.e. the top or front of the plate and a special design of the directly engaging part can contribute to a low-friction or friction-free movement. For this purpose e.g. a mounting on rolls and/or balls can be provided, which can e.g. be fitted to the underside of the actuating element. The term non-contacting mounting of the control element means that the latter can be held without any direct mechanical connection, but it can naturally contact the plate.
Although the restoring or resetting function according to the invention can also be achieved by mechanical means, such as e.g. return springs and the like, it is preferably also brought about in contactless manner. For this purpose the holding device can have at least one, preferably fixed holding magnet and the control element at least one equidirectionally polled magnet. Then e.g. a north pole of the holding magnet facing the plate and a south pole of the magnet facing the plate and the holding magnet can face one another on or in the control element and by means of the relative position with minimum possible, mutual spacing of the magnets define the rest position, in which opposite poles on the holding magnet and control element magnet face one another. The interplay of suitably polled magnets, particularly permanent magnets, on either side of the plate compared with an also possible arrangement with one magnet on one side of the plate and a magnetizable, e.g. ferromagnetic material on the other side, the advantage of a particularly sharp energy minimum of the magnetic field in the minimum spacing area, so that the rest position is particularly reliably and precisely set, even if e.g. frictional forces act against an exact setting.
A particularly secure and energetic holding of the control element and restoring to the rest position is achieved in a preferred development in that the holding device has an inner magnet arrangement with at least one plate-facing, inner magnetic pole and with radial, plate-parallel spacing thereto an outer magnet arrangement of opposite polarity. Through the location of the inner magnet arrangement it is possible to define the rest position of the control element, whilst the outer magnet arrangement substantially assist the guidance and restoring of the slider. Through the opposite polarity of inner and outer magnet arrangements it is possible to ensure that to an attraction towards the rest position brought about by the inner magnet arrangement is added a repulsion of the actuating element towards the rest position brought about by the outer magnet arrangement, so that particularly strong restoring forces are provided. For example, the outer magnet arrangement can be arranged in ring-like and/or rectangular manner around the inner magnet arrangement. A suitable magnetic guidance for the described uniaxial or biaxial, bidirectional slide arrangements can be obtained in that the holding device is constructed for producing a multifold, rotationally symmetrical field of force, particularly a magnetic field and preferably the field of force has a two or four-fold rotational symmetry with the rotation axis perpendicular to the plate.
According to a further development of the invention, the sensor device has at least one sensor on the inside of the plate and which responds to a change to a field, particularly a magnetic, electromagnetic or electric field brought about through an operation of the control element. A sensor can e.g. operate in capacitive, optical or inductive manner. Preferably the sensor device has at least one magnetic field, sensitive sensor, which is placed or is placeable in the working range of a magnet of the control element. It can be a reed contact or switch or a coil. Preferably use is made of Hall sensors, which due to the lack of movable parts operate permanently in a reliable manner and whose output signals in the form of d.c. voltages can be particularly easily and reliably processed. The sensor can be influenced by the same physical phenomenon used for securing the control element, particularly by a magnetic field. Then individual components, such as e.g. a magnet of the control element, can fulfil a double function both in the holding means and also in the sensor device. Embodiments are particularly cost-effective and well adapted to the character of a sliding key in which for each displacement or sliding direction a single sensor is provided, whose output signal indicates a controlling displacement.
According to a further development of the invention, the sensor device has at least two sensors constructed for emitting sensor signals and the control device has at least one logical interconnection unit for the logical interconnection of sensor signals or signals derived from the sensor signals. This makes it possible with relatively few, e.g. only two sensors to set a number of different switching states extending beyond the number of sensors and which result from the states of the individual sensors through logical interconnections, e.g. using the rules Boolean algebra. The sensor device can e.g. cooperate with the control device in such a way that on removing the control element from the plate the appliance is switched into a stable off-state. This creates a manually operable, electromechanical on-off switch, which in particular provides security against unauthorized use, particularly by playing children. The situation can also be such that the sensor device cooperates with the control device in such a way that when the control element is in the rest position the appliance is switched into a readiness state differing from the off state. This standby function can encourage a faster putting into operation should this be necessary, because in the standby function certain fundamental functions can be activated.
These and further features can be gathered from the claims, description and drawings and the individual features, both singly and in the form of subcombinations, can be implemented in an embodiment of the invention and in other fields and can represent advantageous, independently protectable constructions for which protection is hereby claimed.